Reading, writing, and using theorems and definitions.
I think that students should know about the structure of mathematics, by which I mean how and why definitions and theorems are written and what their parts mean. Most of the examples are from calculus, but the ideas apply to all parts of mathematics.
Teaching and Learning Theorems and another Theorems
Definitions and another Definitions
Then there is this – Existence Theorems
Units How to find the units of a derivative or a definite integral